There are a wide variety of wireless communication technologies in use and there are a number of widely used standards. One relatively new standard is known as the “Bluetooth” communication protocol.
The Bluetooth standard defines a technology that allows electronic devices to make wireless connections to another electronic devices. The connections are made without any direct user action. Bluetooth is a relatively short range wireless technology. It is designed to replace cables in devices such as PDAs, cell phones, cameras, speakers, headsets, etc.
The Bluetooth technology utilizes one universal radio link to replace the cables that are normally used to interconnect electronic devices. The key features of the Bluetooth technology are robustness, low complexity, low power and low cost.
Bluetooth was designed for devices that operate in noisy frequency environments. In order to make robust communication links, the Bluetooth uses a fast acknowledgement and frequency hopping. In the United States Bluetooth radios operate at 2.4 GHz in an unlicensed frequency band. Bluetooth minimizes interference by hopping to a new frequency after transmitting or receiving a packet. In general a Bluetooth radio system hops faster and uses shorter packets than do other communication technologies.
The Bluetooth standard includes two levels: First, Bluetooth provides agreement at the physical level. That is, the Bluetooth standard includes a radio-frequency standard. Bluetooth also provides agreement at the next higher level. That is, at the level where products must agree on matters such as, when bits are sent, how many bits will be sent at a time and how the parties to a conversation can be certain that the message received is identical to the message that was sent.
The specifications that define the Bluetooth technology are publicly available on the internet from the web site maintained by the Bluetooth organization. The Bluetooth standard is hereby incorporated herein by reference.
Some Bluetooth systems include an integrated Bluetooth interface in the host. In other Bluetooth devices, the host is connected to a “dongle” by a conventional interface such as by a USB port or by an RS232 port. The dongle then provides a Bluetooth interface to various Bluetooth devices.
An example of a prior art Bluetooth system is shown in FIG. 1. The system illustrated in FIG. 1 has three parts, namely, a host 100, a dongle 101 and Bluetooth external devices (devices A to F as shown in FIG. 1). The dongle 101 and the Bluetooth devices A to F form what is called a piconet. The devices in a piconet share a common communication data channel which is divided into time slots. Each slot is 625 microseconds long. The piconet has a master (which is the dongle) and up to seven slaves. The master transmits in even time slots, the slaves transmit in odd time slots.
The Bluetooth protocol defines various layers. In a Bluetooth system that includes a dongle, the layers in the host interact with layers in the dongle. For example, a conventional Bluetooth system that includes a dongle may have the layers illustrated in FIG. 1. Since the present invention utilizes standard Bluetooth devices, the make up of in the Bluetooth devices is not shown or discussed herein.
As an example, a host and a dongle may have the protocol layers as illustrated in FIG. 1. In the host, the top layer 102 is the application program layer. Program layer 102 is the program layer that ultimately utilizes the data received from the Bluetooth devices A to F and program layer 102 is the layer which generates data that is destined for the Bluetooth devices.
The next layer in the host is the profile layer 104. The Bluetooth specifications defines a wide array of profiles. Profiles describe how various user models can be implemented. A profile describe the minimum implementations of the Bluetooth protocol stack for an application. Manufacturers can add to the profiles defined by the specifications, but each profile defined in the specifications describes a minimum recipe for building a particular type of device. The profile concept is used by Bluetooth to facilitate interoperability between different products from different manufacturers.
The protocol stack 106 is below the profile layer 104. The protocol stack layer 106 defines the set of stacked protocols from lower layers to upper layers. This stack enables devices to locate each other, establish a connection, exchange data and interact with one another through various applications. The protocol stack 106 can for example include the Logical Link Control and Adaptation Protocol (L2CAP), the Service Discovery Protocol (SDP) or the Radio Frequency Communication protocol (RFCOMM). For example, if the L2CAP is used, it controls such things as the transfer of data, disconnecting and timeouts and it takes data from higher protocol layers and applications and it sends the data to lower layers
A Host Control Interface (HCI) layer exists in both the Host and in the dongle. As shown in FIG. 1, the host includes HCI layer 108 and in the dongle includes HCI layer 114. The HCI layer 108 provides the standard protocol for transmitting and receiving packets through the physical link to the dongle. The HCI layer provides a command interface and it provides a uniform method of accessing the Bluetooth baseband capabilities. During the initialization sequence, the HCI layer creates read and write threads, it establishes a connects to the Bluetooth transport, and it resets and reads the device buffers. Once the initialization operations have been completed, the HCI layer enters an initialized state and it is ready to accept clients. HCI command packets, HCI event packets and HCI data packets are transmitted through the interface 150 from the host to the dongle.
The Interface Device Driver Layer 110 and the Interface Device Firmware layer 122 are the layers that provide the actual physical connection between the host and the dongle. This can for example be done using the standard RS232 protocol.
The link manager layer 116 controls link settings such as encryption, power management. Link manger layer 116 also controls the setting of connection conditions such as park, sniff and hold. Finally the Base Band 118 is the physical radio layer in the system. The Base Band Layer 118 manages the physical channels. The baseband protocol works with the link manager 116 for carrying out link level routines like link connection and power control. The baseband also manages asynchronous and synchronous links, and manages the communication scheme.
In the prior art systems, layers such as those shown in FIG. 1, connect one host to one dongle and the dongle in turn communicate with a plurality of Bluetooth devices in a piconet.